U.S. Pat. No. 3,442,808 relates to lubricating oil additives prepared by reacting alkenyl succinic anhydride with the Mannich condensation product prepared by condensing alkyl substituted phenol, formaldehyde and polyalkylene polyamine.
U.S. Patent relates to dispersant- V.I. improver additives prepared by Mannich Base condensation of oxidized ethylene-propylene copolymer with formaldehyde and primary or secondary amines of the general formula: H.sub.2 N(CH.sub.2).sub.y NH.sub.2 (y=3 to 10) and polyalkylene polyamines.
U.S. Pat. No. 4,170,562 relates to modified Mannich reaction products produced by reacting an oxidized ethylene-propylene copolymer with formaldehyde and primary or secondary amines of the general formula: H.sub.2 N(CH.sub.2).sub.y NH.sub.2 (y=3 to 10) and polyalkylene polyamines in the presence of 0.01 to 25 wt % of an oil-soluble phenol of the formula: ##STR1## where R is alkyl of OH, Cl, or Br substituted hydrocarbyl, and y=1 to 5.
U.S. Pat. No. 4,131,553 relates to dispersant/viscosity index improvers prepared by a Mannich Base condensation of an an oxidized ethylene-propylene copolymer with formaldehyde and primary or secondary amines of the general formula: H.sub.2 N(CH.sub.2).sub.y NH.sub.2 (y=3 to 10) and polyalkylene polyamines in the presence of an oil-soluble sulfonic acid as catalyst for the reaction. The sulfonic acids have the general formula: ##STR2## where R is alkyl or OH, Cl, or Br substituted hydrocarbyl, and n=1 to 5. The patent teaches that the sulfonic acid must be added to the oxidized ethylene-propylene copolymer after addition of the amine to avoid rapid decomposition of the acid and darkening of the oil.
U.S. Pat. No. 4,070,402 relates to phenols which are alkylated with high molecular weight ethylene-propylene-diene terpolymers. The alkylated phenols can be converted into ashless dispersants by the Mannich Base reaction with formaldehyde and a polyamine, Bis-aminopropyl piperizine (a diprimary amine) is the only polyamine specified.
U.S. Pat. No. 4,354,950 discloses a method of preparing Mannich base derivatives of hydroxyaryl succinimides of the formula: ##STR3## wherein R is hydrocarbyl of 25 to 200 carbon atoms, R' is H, alkyl or halogen, "n" is 2 or 3, "m" has a value of 1 to 5, Y is H or a methylene hydroxyaryl succinimide radical, "x" has a value of 1 to 2 when Y is H and a value of 1 when Y is a methylene hydroxyaryl succinimide radical. The above succinimides are formed in a stepwise reaction, e.g., by reacting a polyalkenyl succinic anhydride with an aminophenol, to produce an intermediate N-(hydroxyaryl) hydrocarbyl succinimide, which is then reacted with an alkylene diamine and an aldehyde (e.g., formaldehyde) in a Mannich base reaction to produce the described succinimides. The described succinimides may be added to a base oil of lubricating viscosity to form lubricant concentrates and lubricating oil formulations.
U.S. Pat. No. 4,517,104, incorporated herein by reference, discloses polymeric viscosity index (V.I.) improver-dispersant additives for petroleum oils, particularly lubricating oils, comprising a copolymer of ethylene with one or more C.sub.3 to C.sub.28 alpha-olefins, preferably propylene, which have been grafted with acid moieties, e.g. maleic anhydride, preferably using a free radical initiator in a solvent, preferably lubricating oil, and then reacted with a mixture of a carboxylic acid component, preferably an alkyl succinic anhydride, and a polyamine having two or more primary amine groups. Or the grafted polymer may be reacted with said acid component prereacted with said polyamine to form salts, amides, imides, etc. and then reacted with said grafted olefin polymer. These reactions can permit the incorporation of varnish inhibition and dispersancy into the ethylene copolymer while inhibiting cross-linking or gelling.
While these additives are very useful oil compositions, particularly concentrates, thereof tend to exhibit increased viscosity over an extended period of time. Therefore, there exists a need for additives whose oil solutions, particularly oil concentrates, exhibit less viscosity change over an extended period of time.
The source of the viscosity increase over an extended period of time of oil solutions of these additives appears to be, at least in part, due to the chain extension of the polymer. Several solutions to this problem are described in the prior art. One solution is to use the polyamines and then to react the remaining unreacted primary amino groups with acid anhydrides of either C.sub.1 -C.sub.30 monocarboxylic acid, preferably acetic anhydride, or unsubstituted or C.sub.1 to C.sub.8 hydrocarbyl substituted dicarboxylic acid anhydrides of U.S. Pat. No. 4,137,185; or the sulfonic acids of U.S. Pat. No. 4,144,181. These materials act as polyamine group end-capping or inactivating agents to inhibit or limit chain extension. That is to say, the reaction product of the graft copolymer of the ethylenically unsaturated dicarboxylic acid material and polyamine is post-treated with these acid materials to inhibit chain extension and viscosity increase of the imide grafted ethylene copolymer.
While the end-capping or amine inactivating agents disclosed in U.S. Pat. Nos. 4,137,185 and 4,144,181 are generally quite useful, their utilization results in some problems under certain conditions. Thus, for example, reacting a monocarboxylic acid anhydride, e.g., acetic anhydride, with the polyamine yields an acid byproduct, e.g., acetic acid. This acid is deleterious to engine operation, causing corrosion, and generally needs to be removed from the oil solution of the V.I. improver-dispersant. Furthermore, the use of the unsubstituted or lower hydrocarbyl substituted dicarboxylic acid anhydrides of U.S. Pat. No. 4,137,185 generally does not remedy, and may sometimes even contribute to, the formation of haze in oil solutions of the imide grafted ethylene copolymer. This is due to the fact that when using free radical initiators with mineral oil as the grafting medium a proportion of the oil molecules in turn become grafted with the ethylenically unsaturated moiety, e.g., maleic anhydride, and upon subsequent reaction with the amine these grafted oil particles tend to become insoluble and to form haze. Upon the addition of the hydrocarbyl substituted dicarboxylic acid anhydrides to this oil solution to inactivate the unreacted primary amine groups of the imide grafted ethylene copolymer, a certain proportion of the anhydride reacts with the free amine groups of the grafted oil particles. Since the prior art anhydrides are either unsubstituted or lower hydrocarbyl substituted they do not facilitate the solubilization of these insoluble grafted oil particles.
The use of the sulfonic acids of U.S. Pat. No. 4,144,181 may also result in the formation of undesirable acid by-products, e.g., hydrogen sulfide.
Furthermore, these prior art end-capping or primary amine inactivating agents do not, in all instances, provide a sufficient degree of viscosity stability for some applications to oil solutions of the additives of this invention.